The Influence of Tropopause Potential Vorticity Circulation Forcing on the Development of the East Asian Cold Wave in December 2023

In December 14 to 16, 2023, East Asia experienced a severe cold wave, with record-breaking low temperatures and consequently severe natural disasters over broad areas. Results suggest that anomalous downward potential vorticity circulation (PVC) forcing across the tropopause played a critical role in triggering and amplifying this event. The results indicated that in early December, a strong positive potential vorticity substance (PVS) reservoir accompanied by an anomalous downward PVC persisted in the lower stratosphere over Siberia, whereas two distinct upper tropospheric fronts (UTFs) were located over East Asia. By December 12, as the downward PVC penetrated the tropopause into the troposphere, enhancing the northern UTF and triggering a perturbation trough at its western end. This northern trough propagated faster eastward along the UTF than its southern counterpart, and its PVS was intensified by the descending northerly flow. As the two UTFs merged on the eastern Tibetan Plateau, the northern trough was phase-locked with the southern trough, forming a deep East Asian trough with a well-developed PVS. The prominent cold descending northerly flow dominated the troposphere behind the trough, generating extremely high surface pressure and abnormal cold temperature advection below. Consequently, a severe cold wave swept over East Asia. This study improves upon previous work by directly linking tropopause PVC forcing to trough phase-locking, a previously overlooked pathway for cold wave amplification.